Rare earth magnets are widely used as permanent magnets for motors and power generators. Typical examples of the rare earth magnets include sintered magnets and bond magnets each of which is composed of a R—Fe—B-based alloy (R: a rare earth element, Fe: iron, B: boron), such as Nd (neodymium)—Fe—B.
Sintered magnets are each produced by compacting a powder composed of a R—Fe—B-based alloy and then sintering the molded product, and bond magnets are each produced by mixing an alloy powder composed of a R—Fe—B-based alloy with a binder resin and then compacting or injection-molding the resultant mixture. In particular, the powders used for the bond magnets are subjected to hydrogenation-disproportionation-desorption-recombination treatment (HDDR treatment, HD: hydrogenation and disproportionation, DR: desorption and recombination) in order to enhance coercive force.
Sintered magnets are excellent in magnet characteristics because of the high ratio of magnetic phase, but have a small degree of freedom of shape and are thus difficult to form into complicated shapes such as a cylindrical shape, a columnar shape, and a pot shape (cylindrical shape with a bottom). In the case of a complicated shape, cutting of a sintered material is required. On the other hand, bond magnets have a high degree of freedom of shape but have magnet characteristics inferior to those of the sintered magnets. In response to this, Patent Literature 1 discloses that a fine alloy powder composed of a Nd—Fe—B-based alloy is compacted to form a green compact (powder compact), and the green compact is subjected to HDDR treatment to increase the degree of freedom of shape and produce a magnet having excellent magnet characteristics.